Reformate yields by reforming a blend



United States The present invention relates to reforming naphthas and, more particularly, to reforming =a naphtha blend having a controlled ratio of aromatic plus naphthenic hydrocarbons to paraffinic hydrocarbons. That is to say, naphthas having different ratios of aromatic plus naphthenic hydrocarbons to paraifinic hydrocarbons, i.e., different A+N/ P ratios are mixed to provide a blend having an A-l-N/P ratio in a critical range and the blend is reformed under reforming conditions of temperature, pressure, and liquid hourly space velocity to provide a reformate having the required or target octane rating (Research-k3 cc. TEL). It has been found that the yield of C and heavier reform-ate produced when reforming a blend having an A-l-N/P ratio in the critical range is greater than the yield of C and heavier reformate when the naphthas each having an A-i-N/P ratio outside of the critical range are reformed separately to the target octane rating and the reformates blended.

Data are available establishing that when reforming a naphtha having a low A+N/P ratio, i.e., Ia paraffinic naphtha, more dehydrocyclization occurs than when reforming a naphtha having a high A-I-N/P ratio, i.e., a naphthenic naphtha. Thus, when reforming a paraffinic naphtha, i.e., a naphtha having an A-l-N/P ratio of 0.74 the number of ring compounds, i.e., aromatic plus naphthenic hydrocarbons in the reformarte is greater than the number of ring compounds in the charge. For example, when a Mid-Eastern naphtha having a concentration of aromatic plus naphthenic hydrocarbons of about 40 mol percent is reformed under conditions of temperature, pressure, and liquid hourly space velocity to produce a C and heavier reformate having an octane rating (Research-{6 cc. TEL) of about 104 the concentration of ring compounds, i.e., aromatic plus naphthenic hydrocarbons is increased to about 76 mol percent. This increase of ring compounds is indicative of a considerable amount of formation of ring compounds from straight-chain compounds, i.e., by dehydrocyclization of the paraflinic hydrocarbons in the feed.

On the other hand, there are data showing that considerable ring-cracking occurs when a stock rich in ring compounds, i.e., having a high A-l-N/P ratio is reformed. Thus, a naphtha having an A +N/P ratio of 2.93 had a concentration of ring compounds of 74 mol percent. When this naphtha is reformed under conditions of temper-ature, pressure, and liquid hourly space velocity to produce C and heavier reformate having an octane rating (Research-H cc. TEL) of 104 the concentration of ring compounds decreases from the aforesaid 74 mol percent to about 70 mol percent. Since the octane ratings of reformates are predominantly dependent upon the concentration of aromatic hydrocarbons in the reformate, it follows that reformate yields are dependent upon ring formation. Hence, yield advantages can be obtained when the ratio of the concentration of aromatic plus naphthenic hydrocarbons to parafiinic hydrocarbons is adjusted to be in a critical range in which the dehydroatent cyclization of paraflinic hydrocarbons is maximized and the hydrocracking of naphthenic hydrocarbons is minimized.

it has been found that a blend of two or more naphthas or fractions thereof, at least one of which has a high A+N/P, i.e., R-S ratio or at least one of which has a low RS ratio or one of which has a high R-S ratio and one of which has a low R-S ratio to provide a blend having an R-S ratio in a critical range and reforming the blend under reforming conditions of temperature, pressure, and space velocity to produce C and heavier reformate having the target octane rating (Research-H cc. TEL) produces a greater yield of C and heavier, C and heavier, and C and heavier reformate than is produced when the naphthas or fractions of naphthas are reformed separately to the same target octane and the reformates blended.

It is recognized that blends of naphthas have been reformed heretofore. However, these prior art practices are not to be confused with the method of the present invention since none of the prior art methods involved blending of two or more naphthas having different R-S ratios to provide a blend having an RS ratio in a critical range. Thus, in U.S. Patent No. 2,- 691,623 the patentee describes a method treating crude oil to obtain various gasoline fractions including virgin naphtha and cracked naphtha. The feed to the reforming unit consists of cracked naphtha and sufficient of straight run naphtha to provide sufficient hydrogencontaining reformer make-gas to satisfy the requirements of the dcsulfurizing unit for hydrogen.

In US. Patent No. 2,971,902 the patentees describe a method of aromatizing hydrocarbons in which C to C paraffins are mixed with a naphthenic hydrocarbon feed in an amount within the range of about 0.1 to about 2.0 mols of C to C paraflinic hydrocarbons per mol of feed hydrocarbon. Thus, it is manifest that these patentees do not suggest that improved results can be obtained by adjusting the R-S ratioin a critical range but teach to adjust the ratio of the concentration of light paraffins to the concentration of ring compounds plus paraflinic hydrocarbons.

In US. Patent No. 2,773,008 a method of hydrodesulfurizing a mixture of virgin naphtha and cracked naphtha, separating a reformer feed from the efiiuent of the hydrodesulfurizer and reforming the aforesaid reformer feed is described. The virgin naphtha is mixed with the cracked naphtha in the ratio of about 1.626 barrels of virgin naphtha per barrel of cracked naphtha. Since the concentrations of aromatic, naphthenic, and parafiinic hydrocarbons in the virgin and cracked naphthas are not given, it is manifest that this teaching cannot be con-' fused with the present method of blending naphthas to provide a blend having an R6 ratio in a critical range.

In US. Patent No. 2,946,737 the patentee describes a method for increasing the yield of gasoline having an octane rating (Research+3 cc. TEL) in excess of wherein the reformer feed is contacted in a plurality of reaction zones in which the catalyst is distributed in a manner to charge the first reaction zone with the minimum quantity of particle-form solid reforming catalyst to produce the maximum difference between the vapor inlet temperature and the vapor outlet temperature of the first reaction zone while the balance of the reaction zones is charged with the amount of catalyst required to produce the required octane rating without distributing the catalyst in the balance of the reaction zones in a critical manner.

It is also old in the art to introduce into the reaction zone, particularly the reaction zone in which the endothermic reaction of the dehydrogenation of naphthenes is the predominating reaction, an amount of heated olefinic hydrocarbons the exothermic heat of the hydrogenation of which will balance the loss of heat due to the endo thermic dehydrogenation reaction. However, those skilled in the art will recognize that none of these prior art manipulations is dependent upon blending two or more naphthas or naphtha fractions in a manner to provide a naphtha blend or reformer feed having a critical R-S ratio.

When reforming first became a major tool of the petroleum refine-r whereby the industry sought to meet the demand for gasolines having higher octane ratings, economic considerations resulted in limiting reformer feeds to low octane straight run stocks. Subsequent developments including restrictions on the maximum olefin content of the gasoline sold for use on the public roads has made it necessary to consider thermal naphthas, and catalytically cracked naphthas for use as reformer charge stocks or for upgrading by other means.

Thus, for example, it has become necessary to reform catalytically cracked naphtha having the following composition and being the 250 to 380 P. fraction of gasoline produced by catalytic cracking.

Percent;

b percent Components Y Volume Paraffins Naphthenes Aromatics Others Octane Number:

(R+ ml.) (3+3 ml. TEL) 'When the foregoing fraction of catalytically cracked naphtha (naphtha A) was reformed in the presence of hydrogen and platinum-group metal reforming catalyst com-prising 0.6 percent by weight of platinum and 0.7

' percent by Weight of chlorine on alumina support under 500 .p.s.i.g. pressure and reforming conditions of temperature (vapor inlet) and liquid hourly space velocity (volume of naphtha/hour/volume of catalyst, i.e., v./hr./v.) to produce C and heavier reformate having an octane rating of 103.1 (Research+3 ml. TEL) the yield of C and heavier reformate was 92.7 percent by volume based upon the naphtha charged to the reforming unit.

When a 250 to 380 F. fraction of Mid-Continent naphtha (naphtha B) having the properties set forth hereinafter was reformed in the presence of hydrogen and a platinum-group metal reforming catalyst having substantially the samecomposition as that used in reforming the catalytically cracked gasoline at a pressure of 500 p.s.i.g. and under reforming conditions of temperature and liquid hourly space velocity to produce C and heavier reformate having an octane rating of 103.1 (Research-F6 ml. TEL) the yield of C and heavier (C reformate was 85 percent by volume based upon the naphtha charged to the reforming unit.

4 The 250 to 380 F. Mid-Continent naphtha had the following characteristics:

It will he observed that the ratio of the mols of aromatics plus the mols of naphthenes to the mols of parafiins in the aforesaid naphtha A is 2.06

while the ratio of mols of aromatics plus mols of naphthenes to mols of parafiins in the aforesaid naphtha B is 1.30 (437+126/432:56.3/43.2=-1.30).

It has now been discovered that the overall yield of C.;+, (3 and (3 reformate from naphthas having a ratio of aromatic-s plus naphthenes to parafiins outside the range of 1.35 to 1.60 can be improved an industrially important amount by reforming a blend of two or m re naphthas or naphtha fractions which blend has an R-S ratio in the range of 1.35 to 1.60 and preferably in the range of 1.40 to 1.55 when compared with the overall yield when the naphthas are reformed separately and the reformates blended to the same blend octane rating. The aforesaid blend comprises at least one naphtha or naphtha fraction having an R-S ratio outside the range of 1.35 to 1.60. The naphthas or naphtha fractions are mixed in proportions dependent upon the individual f R-S ratios to provide a naphtha blend and reformer feed having an R-S ratio in the aforesaid ratio of 1.35 to 1.60 and preferably in the range of 1.40 to 1.55.

Accordingly, the present invention provides .for mixing naphthas having a ring-to-straight chain ratio, i.e., the ratio of mols of aromatics plus mols of naphthenes to the mols of parafiins, greater or less than 1.35 to 1.60, in a proportion to provide a reformer blend charge having a ring-to-straight chain ratio in the range of 1.35 to 1.60 and preferably in the range of 1.40 to 1.55 and reforming the reformer blend charge under reforming conditions of vapor inlet temperature and liquid hourly space velocity, dependent upon the activity of the reformer catalyst employed, to provide a C reformate having an octane rating of at least lOO'.

illustrative of naphthas having a ring-to-straight chain, i.e., R-S ratio, in excess of 1.60 are catalytically cracked naphthas, thermally cracked naphthas, and virgin naphthas from crudes such as Wilmington crude having a naphthene content of about 61 percent by volume and a naphthene plus aromatics content of about 74 mol percent.

Illustrative of naphthas having a \S ratio less than 1.35 are naphthas from Mid-Continent crudes, naphthas from Mid-Eastern crudes, and raflinates from solvent extraction with solvent having a greater solubility for more aromatic hydrocarbons than for more paraffinic hydrocarbons and sonbates from the fractionation of mixtures containing normal paraffins and at least one of naphthenes, aromatics, and isoparaffins by zeolites, industrially designated molecular sieves.

Thus, for example, a fraction of naphtha from Wilmington crude having a boiling range (ASTM) of 5 to 350 F. and the following composition has an R-S" ratio of 2.913.

Naphtha C (California mix, 190-350" F.)

Percent M01. Components y percent Volume Paraffins 28. 8 25. 3 Nanhthenes 61. 3 63. 1 Aromatics.-. 9. 4 11. 1 Others 0. 5 0. 5

63. 11.1 74.2 R-S rat1o=- =2.93

25.3 '253 Illustrative of Mid-Eastern naphthas is the fraction of Kuwait naphtha having a boiling range (ASTM) of 220 to 380 F. and the following composition:

Illustrative of rafiinates and sorbates is the raflinate from the solvent extraction of Mid-Continent Reformate having an octane rating of 98 (R+3 ml.) with diethylene glycol and having the following characteristics:

Naphtha E (raflinate) [Boiling range, F., 187 to 389] Percent M01. Components y percent Volume Parafiins 86. 6 85. 0 N aph 4. 4 5. 0 Aromatics 9. 0 10. 0

Others 5 .0 10.0 15 .0 R- r t1o===0.18

Illustrative of the blend reformer charge stocks to be reformed as described herein are the following:

Vol. R-S Blend Components Percent Ratio" R-S Ratio N aphtha A 28 2. 06 N aphtha B. 72 1.30 1. 48 N aphtha O. 55. 6 2. 93 Naphtha D. 44. 4 0. 74 1. 60 Naphtha C 69.7 2.93 Naphtha E 30. 3 0. 18 1. 35

Thus, naphtha D being the 220 to 380 F. fraction of Kuwait naphtha and having the composition set forth hereinbefore was reformed at 500 p.s.i.g. at reforming conditions of vapor inlet temperature and liquid hourly space velocity in the presence of hydrogen and platinumgroup metal reforming catalyst to produce a C and heavier (C reformate having an octane number of 105 (Research-F3 ml. TEL) in a yield of 67.4 percent by volume on the charge naphtha C being the 190 to 350 P. fraction of California Mix naphtha and having the composition set forth hereinbefore was reformed at 500 p.s.i.g. at reforming conditions of vapor inlet temperature and liquid hourly space velocity in the presence of hydrogen and platinum-group metal reforming catalyst to produce a 0 reformate having an octane number of (Research+3 ml. TEL) in a yield of 79.1 percent by volume on the charge.

When the reformates of naphthas D and C are blended in the ratio of one volume of each, the overall yield is 73.3 percent by volume. On the other hand, when one volume of naphtha C is blended with one volume of naphtha D to provide a blend reformer charge which is reformed at 500 p.s.i.g. and at a temperature (vapor inlet) and liquid hourly space velocity in the presence of hydrogen and platinum-group metal reforming catalyst to produce C reformate having an octane rating (Research+3 ml. TEL) of 105 the yield is 74.2 percent by volume on the charge. This is an increase in yield of 0.9 percent in the overall yield.

Blend: 1 volume of naphtha C-l volume of naphtha D Those skilled in the art will recognize the foregoing to be a description of a method of reforming hydrocarbon mixtures boiling in the range of about to about 550 F. preferably in the range of about 180 to about 410 F. in the presence of hydrogen and particle-form solid reforming catalyst under reforming conditions of temperature, pressure and space velocity to maximize the conversion of naphthenic hydrocarbons and paraifinic hydrocarbons to aromatic hydrocarbons and to minimize the hydrocracking of naphthenic and paraffinic hydrocarbons. Reaction temperature, as measured at the vapor inlet of the reaction zone(s) is in the range of 800 to about 1050 F. Reaction pressure is in the range of 15 to 1,000 p.s.i.g. Space velocity is in the range of 0.5 to 20. Hydrogen-to-reformer feed ratio is in the range of l to 20 mols of hydrogen per mol of reformer feed or naphtha blend. While any particle-form solid reforming catalyst can be used as a static bed or beds or in accordance with moving bed or fluidized techniques, it is presently preferred to employ a reforming catalyst comprising platinum-group metal on a refractory oxide support and particularly a reforming catalyst comprising about 035 to about 0.6 percent by weight of platinum on alumina with or without about 0.1 to about 0.8 percent by weight of halogen. When employing a platinum-group metal reforming catalyst comprising about 0.35 to about 0.6 percent by weight of platinum and about 0.4 to about 0.7 percent by weight of chlorine and reforming a C to 370 F. end point naphtha it is preferred that the naphtha contain not more than innocuous concentrations of sulfur, nitrogen, and arsenic which are respectively 200 p.p.m., 1 p.p.m. and 2 p.p.b. (P.p.m. is parts per 10 parts of naphtha and p.p.b. is parts per 10 parts of naphtha.) The reformer feed is contacted with the platinum-group metal catalyst in the presence of hydrogen at reforming conditions of temperature, pressure, and space velocity dependent upon the activity of the catalyst and the required, or target octane rating (Research+3 cc. TEL) of the C and heavier (C reformate. Preferably, the reformer feed having an R-S" ratio in the range of 1.35 to 1.60, preferably in the range of 1.40 to 1.55 is contacted with the particle-form solid reforming catalyst under reforming conditions of tem perature, pressure, and space velocity to produce a C reformate having an octane rating (Research-H cc. TEL) 7 of at least 100, and separating from the reformer efiiuent comprising hydrogen and C and heavier hydrocarbons a C r'eformate having an octane rating (Research+3 cc. TEL) of at least 100.

I claim:

1. A method of reforming hydrocarbon mixtures having an R-S ratio outside the range of 1.35 to 1.60 which comprises mixing at least two hydrocarbon mixtures boiling in the range of about 180 F. to about 550 F. at least one of which has an R-S ratio outside the range of 1.35 to 1.60 in proportions to produce a blend having an R-S ratio in the range of 1.35 to 1.60, reforming said blend in the presence of hydrogen and particle-form solid reforming catalyst at reforming conditions of temperature, pressure, and space velocity to maximize conversion of naphthenes and paraffins to aromatics and to minimize hydrocracking of naphthenes and paraffins, obtaining a reformer effluent comprising hydrogen and C and heavier hydrocarbons, and recovering C reformate therefrom.

2. The method set forth in claim 1 whereinthe reforming catalyst is platinum-group metal reforming catalyst, and wherein the blend contains not more than innocuous concentrations of sulfur, nitrogen, and arsenic.

3.-The method set forth in claim 2 wherein the reforming catalyst comprises about 0.35 to about 0.6 percent by weight of platinum, and about 0.4 to about 0.7 percent by weight of chlorine on alumina support.

4. The method of claim 1 wherein the first hydrocarbon mixture has an RS ratio of about 2 and the second hydrocarbon mixture has an R-S ratio of about 1.30.

5. The method of claim 1 wherein the reformer charge has an R-S ratio in the range of 1.40 to 1.55 and wherein the platinum-group metal reforming catalyst comprises about 0.35 to about 0.6 percent by weight of platinum and about 0.4 to about 0.7 percent by weight of chlorine on alumina support.

6. The method of claim 1 wherein at least during dehydrogenation of the naphthenes the difference between the vapor inlet temperature of the reformer charge and the temperature of the reaction products is not more than about 50 F. whilst a major portion of the naphthenes of the charge is converted.

7. method of reforming hydrocarbon mixtures boiling in the range of about 180 to about 410 P. which comprises blending a first hydrocarbon mixture boiling in the range of about 180 F. to about 410 F. comprist5; ing naphthenes and aromatics and having an R-S ratio greater than 1.60 with a second hydrocarbon mixture boiling in the range of about 180 F. to about 410 F. comprising paraffin and having an R-S ratio less than 1.35 to form a reformer charge having an R-S ratio in the range of 1.35 to 1.60 and containing not more than 200 ppm. of sulfur, not more than 1 ppm. of nitrogen, and not more than two parts of arsenic per 10 contacting said reformer charge with platinum-group metal reforming catalyst in the presence of hydrogen at reforming pressure and reforming conditions of temperature and liquid hourly space velocity to produce a C reformate having an octane rating (Research-l-3 ml. TEL) of at least 10 0, obtaining a reformer effluent comprising hydrogen and C and heavier hydrocarbons, and separating from said reformer effluent C reformate having an octane rating (Research+3 cc. TEL) of at least 100.

8. The method of claim 7 wherein the platinum-group metal reforming catalyst comprises about 0.35 to about 0.6 percent by weight of platinum on refractory oxide support.

.9. The method of claim 7 wherein the platinum-group metal reforming catalyst comprises about 0.35 to about 0.6 percent by weight of platinum on alumina.

10. The method. of claim 7 wherein the first hydrocarbon mixture has an RS ratio of about 2 and the second hydrocarbon mixture has an R-S ratio of about 1.30.

11. The method of claim 7 wherein the reformer charge has an RS ratio in the range of 1.40 to 1.55 and wherein the platinum-group metal reforming catalyst comprises about 035 to about 0.6 percent by weight of platinum and about 0.4 to about 0.7 percent by weight of chlorine on alumina support.

12. The method of claim 7 wherein at least during dehydrogenation of the naphthenes the difierence between the vapor inlet temperature of the reformer charge and the temperature of the reaction products is not more than about 50 F. whilst a major portion of the napht'nenes of the charge is converted.

References Cited in the file of this patent UNITED STATES PATENTS 2,416,894 Barron Mar. 4, 1947 2,427,800 Mattox Sept. 23, 1947 2,955,080 Carter Oct. 4, 1960 2,971,902 Blome et al Feb. 14, 1961 

1. A METHOD OF REFORMING HYDROCARBON MIXTURES HAVING AN "R-S" RATIO OUTSIDE THE RANGE OF 1.35 TO 1.60 WHICH COMPRISES MIXING AT LEAST TWO HYDROCARBON MIXTURES BOILING IN THE RANGE OF ABOUT 180*F. TO ABOUT 550* F. AT LEAST ONE OF WHICH HAS AN "R-S" RATIO OUTSIDE THE RANGE OF 1.35 TO 1.60 IN PROPORTIONS TO PRODUCE A BLEND HAVING AN "R-S" RATIO IN THE RANGE OF 1.35 TO 1.60, REFORMING SAID BLEND IN THE PRESENCE OF HYDROGEN AND PARTICLE-FORM SOLID REFORMING CATALYST AT REFORMING CONDITIONS OF TEMPERATURE, PRESSURE, AND SPACE VELOCITY TO MAXIMIZE CONVERSION OF NAPHTHENES AND PARAFFINS TO AROMATICS AND TO MINIMIZE HYDROCRACKING OF NAPHTHENES AND PARAFFINS, OBTAINING A REFORMER EFFLUENT COMPRISING HYDROGEN AND C1 AND HEAVIER HYDROCARBONS, AND RECOVERING C4+ REFORMATE THEREFROM. 